By CHARLES A. BERRY, M.D., Chief, Center Medical Operations Office, NASA Manned Spacecraft Center


[199] Summary


The lessons learned from the operational medical program conducted in Project Mercury are discussed in this paper.


The objectives of the medical portion of the crew selection program were met, and detailed physical examinations on even select test pilot groups have found rejectable defects. Stress testing has been made part of a selection-in-depth training program.


Medical training given to the astronauts has been of great value during inflight monitoring and discussion of medical problems.


Medical maintenance has included routine medical care, and annual and special physical examinations. Close association of the flight surgeon and the astronaut in training has produced an excellent preventive medicine practice. The flight crew surgeon is best fitted to determine the astronaut's readiness for flight, but a specialist team conducts the examination for baseline data to compare with postflight data. Preflight examinations were conducted before each checkout procedure and more formally at 10 days and 3 days before flight, and on flight morning. Longer missions with Pacific recovery caused modification of the postflight examinations. The importance of practice runs of most of the medical procedures was shown and a medical countdown was developed and integrated with the Mercury Control Center (MCC) and blockhouse countdown.


Complete isolation of the crew is impractical and has depended on n reduction of stronger contacts in the immediate preflight period.


Drugs were provided in injectors, and pills were available in flight and the survival kit. The only drug used was the dextro-amphetamine sulfate on the MA-9 mission. The astronaut must always be pre-tested to any drug he may use. Scheduling of rest, activities? and exercise periods is necessary. A method of obtaining separate urine samples was successfully used. Dietary control of defecation was successful. Inflight food and water ingestion must be scheduled.


Medical monitoring was performed for flight safety reasons and for aiding the surgeons in making go-no go recommendations to the operations director. The value of range flight simulations and of the medical flight controller has been shown. Parameters monitored included body temperature, respiration, electrocardiograph, blood pressure, and voice. The comparison and correlation of readings with environmental data are stressed. Correlation of inflight events and physiological responses is very meaningful. The space-flight environment, while exposing men to numerous stresses, has produced no unmanageable physiological overload. postflight orthostatic hypotension has been noted for a period of several hours.


Recovery operations have been modified from taking medical care to the astronaut to taking the astronaut to medical care. The support has been trimmed to require fewer highly trained personnel to "wait it out" at the launch site.


Project Mercury gave the opportunity to define more closely the medical problem areas as the future is anticipated with great expectations and confidence in man's ability to adapt to and conquer this new frontier.




The development of an operational medical program for Project Mercury posed a challenge to the national aerospace medical community in line with that which the orbiting of man posed to the national engineering community. The purpose of this paper is to review briefly and necessarily incompletely the medical operations and findings from all our manned space flights and to emphasize the knowledge [200] required which may be applied to future programs. Details of the operational procedures and findings are documented in the several reports of the Mercury missions (refs. 1 to 12).


The nature of the challenge called for the development of some ground rules applicable to the medical aspects. It was determined that:

(1) The simplest and most reliable approach should be used.

(2) Off-the-shelf items and existing technology should be used wherever possible.

(3) Man was being thrust into a truly unknown environment, and his reactions to this environment were relatively unknown.

(4) A direct approach would be taken to the problem areas, and attempts would be made to provide the best protection and monitoring capable within the operational constraints of the mission.


Many lessons have been learned from this first experience of the free world with manned space-flight operations. The responsible medical community had honestly attempted to evaluate potential problems based upon knowledge at that time. In doing this, several possible problems were raised which, it appears, this program has answered to some degree. Weightlessness is a good example of the many barriers to man's entry into space which were raised prior to this program. Some of the dire physiological effects predicted as a result from exposure to this condition and therefore to be limiting to space flight were anorexia, nausea, disorientation, sleepiness, sleeplessness, fatigue' restlessness, euphoria, hallucinations, decreased g-tolerance, gastrointestinal disturbance, urinary retention, diuresis, muscular incoordination, muscle atrophy, and demineralization of bones. It will be seen that few of these remain of concern. Another area in which there were predictions of undesirable effects is in the psychological response to the isolation of space. The astronauts to date have not been isolated in space and have generally complained of too much earth contact. There has been no evidence of any breakoff phenomenon or aberrent psychological reaction of any sort. Thus, while no serious problems have developed, more information is needed on increased time periods in space and the conclusions of the present paper can only be based upon the duration of flights thus far flown. Each mission has been used as a means of evaluating the next step into space, and it is believed that the six manned missions in this program have laid the groundwork for future programs. Project Mercury gave the opportunity to define more closely the medical problem areas, and the future is anticipate with great expectations and confidence in man' ability to adapt to and conquer this new frontier.


Crew Selection and Training


The medical portion of the selection program had as its objectives the provision of crew members who (1) would be free of intrinsic medical defects at the time of selection, (2) would hare a reasonable assurance of freedom from such defects for the predicted duration of the flight program, (3) would be capable of accepting the predictable psycho-physiologic stress of the missions, and (4) would be able to perform those tasks critical to the safety of the mission and the crew. The selection board found themselves viewing already trained test pilots somewhat in the same manner as cadets entering a training program are viewed. Small numbers were selected, leaving little excess for attrition; In view of these objectives, the group was culled by records review, interview, and testing until a final group was given a rigorous medical examination at the Lovelace Clinic in Albuquerque, New Mexico. This examination was followed by a stress-testing program at Wright Patterson Air Force Base, Ohio. The results of these examinations were reviewed by the participating physicians, and the candidates were given a medical rank order. This rank order was then presented to a board which selected the original seven astronauts. In retrospect, it can be said that the results of this program were adequate in view of the fact that the assigned astronauts have successfully completed their flight missions. This early program has been of assistance in the development of current selection program. The stress-testing in the initial selection efforts has been deleted since it was found to be of little value in a group who had already been very thoroughly stress-tested by virtue of their test-pilot background. Stress-testing has become a part of the training program with a selection in depth carried on during the training. Thus, each exposure is mission-oriented and further is an additional [201] selection test as well as providing baseline medical information. In the current programs, this technique is being used; and the astronauts understand that they are continually undergoing selection and that there may be attrition.


The premise that detailed physical examinations given to groups as select as test pilots will show up many physical defects which would interfere with a reasonable prediction of career length in the manned space-flight program has been confirmed in this program.


The training program has included a series of lectures on the anatomy and function of the human body, and the series has proven to be of great value during inflight monitoring and discussion of potential medical problems. Every attempt has been made to use engineering analogies where possible and to impress the flight crews with the fact that the human organism and its many systems must be monitored as thoroughly as many of the engineering systems if mission success is to be assured. There has been no formal physical training program but each astronaut has been charged with maintaining his fitness through programed exercise of his choice. A wide variety has been used by the group. Medical advice was offered and the importance of regular training periods was stressed during the preflight preparation period. A plateau should be reached and, although no specific level is specified, it is believed the astronaut is better prepared to withstand the flight stresses if he maintains a state of physical fitness.


Medical Maintenance and Preflight Preparation


The medical maintenance during this program consisted of the routine medical care similar to that provided specialized groups of aircraft pilots, annual physical examinations, and special physical examinations performed before procedures such as altitude-chamber runs, pressure- suit indoctrinations, and centrifuge runs. The flight schedule with its necessary preflight spacecraft checkout procedures, simulated flights, and launches, frequently exposed each flight crew member to several physical examinations within a given year. An attempt was made to make these physical examinations serve several purposes such as qualifying the individual for his annual physical, being ready to participate in a given procedure, and collecting baseline data. A close and frequent contact between flight crews and flight surgeons, with the flight surgeons monitoring participation in all stress exposures and training exercises, proved to be extremely valuable preparation for the flight mission. This close association also provided excellent preventive medicine practice among the flight crews. It is thought that the flight crews have certainly had no more illness than what would be expected in a routine pilot population; and the general feeling is that there was probably much less.


The preflight physical examinations were to serve two basic purposes. First, they should allow the flight surgeon to state that the astronaut was qualified and ready for flight. Second, they should provide a baseline for any possible changes resulting from exposure to the spaceflight environment. The flight crew surgeon appears best qualified to determine whether the astronaut is medically reedy for flight. Early in the program, the search for unexpected changes in body systems as a result of exposure to space flight dictated specialty examinations of various body systems. A team was assembled from the Department of Defense and included specialists in internal medicine, ophthalmology, neurology, psychiatry, and laboratory medicine. The same specialties have continued to be represented, but certain items of the examinations have been modified as knowledge of the lack of serious effects of flight on the astronaut was gained. Prior to the selection of a flight astronaut for a given mission, the medical records of those. being considered are reviewed in detail and a medical recommendation given to the operation director. Following experience on the early missions, it was determined that a thorough evaluation of the flight astronaut would be made 10 days prior to the scheduled mission to assure management and the flight director that the astronaut was indeed ready for the mission. This examination included a medical evaluation of both the flight astronaut and his backup. Three days prior to the mission, the detailed physical examination was completed by the various medical specialists and the necessary laboratory work was accomplished. On flight morning, following a brief medical examination, a final determination was [202] made as to the readiness of the astronaut for flight. This examination was principally concerned with noting any recent contraindications to flight which may have developed. While early in the program other specialists participated in this examination, on the last two missions: the participation was reduced to that by the flight crew surgeon.


The postflight medical examinations were initially made by the Department of Defense recovery physicians stationed aboard the recovery vessel. On the early mission, the astronaut was then flown to Grand Turk Island and was joined there by the team of medical specialists who had made the preflight examination and by the flight crew surgeon. As the flights became longer and recovery was accomplished in the Pacific Ocean, the plan was changed and one of the NASA flight surgeons was predeployed aboard the recovery carrier to do the initial postflight examination and debriefing. On the MA-8 mission, the Director of Medical Operations and the medical evaluation team deployed to the Pacific recovery site several hours after recovery, and this was not only a tiring experience, but necessitated that a great deal of the examination and debriefing be done prior to their arrival. The detailed postflight specialty examination was then conducted at Cape Canaveral when the astronaut returned from the recovery site. In some instances, this practice required the teaching of special techniques to the flight surgeon in order that early information could be obtained. Project Mercury has been most fortunate in having rapid postflight recovery and examination of the flight astronauts, allowing excellent comparison of postflight with preflight data. It would seem from our experience that the retention of any specialty examination team at a mainland launching or debriefing site would be the preferable plan of action.


Early in the preflight. preparations, it was determined that there was a need for many practice runs of various procedures. These runs were accomplished by doing. the actual flight-type preparation for centrifuge runs, spacecraft checkout runs in the chamber at Hanger S, simulated flights and launches, and procedures trainer exercises. The Mercury Redstone suborbital flights were also extremely helpful in preparation for orbital flight. A medical countdown was developed with specific timing of the various events and coordination with the blockhouse and range countdown. In order to have no delay in the scheduled launch, a great deal of practice in this countdown was necessary. It has continued to pay dividends in the later missions. Backup personnel in the various medical areas are needed just as backups are needed for the various pieces of equipment. Experience has allowed the number of backup personnel to be kept to an absolute minimum.


Prior to the first launch, consideration was given to the necessity for isolating the flight crew in order to prevent the development of some communicable disease immediately prior to or during flight. It soon became evident, however, that such isolation was impractical in view of the numerous requirements upon the flight crew during the 2 weeks prior to launch. . Many activities required the presence and participation of the astronaut, and the isolation was reduced to attempts to curtail the number of contacts with strangers. As the missions get longer and longer, the situation may have to be re-evaluated since the mission could last longer than the incubation period of some diseases. No difficulty was encountered during the Mercury program with the use of only a very modified isolation plan.


One of the basic concepts developed stated that there would be no drugs used as routine measures, but that drugs would be made available for emergency use. Injectors were made available which could deliver their contents through the pressure suit into the astronaut's thigh. During the first four missions, the drugs available in the injectors included an anodyne, an antimotion sickness drug, a stimulant, and a vasoconstrictor for treatment of shock. In the later missions, this was reduced to the antimotion sickness drug and an anodyne, available both on the suit and in the survival kit. An evaluation of the longer mission programed for MA-9 led to the decision to make available tablets of dextro-amphetamine sulfate, both in the suit and in the survival kit. Antimotion sickness and antihistamine tablets were also made available. The astronaut's mental and physical integrity were never in doubt during the mission. As the time for retrofire approached, a review of the mission tasks made [203] it evident that the astronaut had undergone a long and rigorous work schedule from which he might be expected to experience considerable fatigue, even assuming ideal environmental conditions and full benefit from restful sleep. As has been reported, medication was used for the first time during flight when the dextro-amphetamine sulfate was taken prior to the initiation of retrosequence. Such drugs should be available and plans must be made for their availability both during flight and postflight in the survival kit. The astronaut must always be pretested for effect of the drugs which will be used.


Experience has shown that care must be taken to prevent astronaut fatigue during the final preflight preparations as well as postflight. Many individuals have matters of importance which must be decided by the astronaut during the final week of preparation; and as launch day grows closer, the demands on the astronaut's time increase. Careful scheduling of rest, activities, and exercise periods are needed; and much more e attention must be paid to this scheduling in future missions. Since the effects of these variables were unknown, it was the flight surgeon s decision to administer 5 mg of dextro-amphetamine sulfate to the astronaut in order to increase the probability of peak performance during reentry. Experience has shown that 48 to 72 hours is a minimum time for a postflight rest and relaxation following a 34-hour mission. Seventy- two hours should be a minimum for future missions.


Early missions required only simple provisions for the collection of urine and blood samples. The short-mission durations made it entirely feasible to collect all the voided urine in a single container within the suit and to recover it after astronaut recovery. As mission duration increased, this became an unworkable procedure; and further, there was a desire to obtain separate urine samples for analysis. The last mission utilized a system for collecting five separate and complete urine samples for later evaluation. This system worked properly but will require modification for future missions. No blood samples have been obtained during flight. Every attempt has been made to combine the various blood requirements in order to require as few vena punctures as possible both preflight and postflight.


Early in the preparation period, a medical flight plan is developed and integrated with the overall mission flight plan. A good deal has been learned about realistic sampling in light of flight plan and in utilizing normal operational activities and reports as means of medical evaluation.


Dietary control has been utilized for approximately 1 week prior to each mission. The first several days were used to assure a normal balanced diet during the rather hectic preflight preparations. In order to prevent defecation during the mission, the low-residue diet was programmed for 3 days prior to launch, and the time extended if the launch was delayed. This diet performed its task very satisfactorily during the entire Mercury program; still, indications are that any more prolonged period would seem unwise. The inflight food has consisted of the bite-size and semi-liquid tube food on the early missions. On the last mission, the freeze-dehydrated food was added. Problems with crumbling have been encountered with the bitesize food, and difficulty in hydrating the freeze dehydrated food was encountered on the last mission. The assurance of palatable food is necessary, and proper containers and practice in their use appear indicated. It also appears necessary to schedule food and water intake on the flight plan and to check to see that it has been properly accomplished.


Medical Monitoring


The Mercury program provided the free world with the first opportunity for full-time monitoring of man in the space-flight environment. At the start of this program, the continuous monitoring of physiological data from a pilot conducting a mission was a very recent concept. it the time, there were no off-the-shelf items available to allow continuous and reliable physiological monitoring. It was decided to attempt to monitor body temperature, chest movement, and heart action (ECG). Standards required that the sensors and equipment be comfortable, reliable, compatible with other spacecraft systems, and would not interfere with the pilot's primary mission.


It should be realized that the biomedical sensors are used as a means of flight-safety monitoring. The primary purpose is to assist the [204] monitoring flight surgeon in determining whether the astronaut is capable of continuing the mission from a physiological point of view. The information is used as a basis for making go-no-go decisions in the control center. No attempt has been made under the current operational conditions to perform detailed system evaluation or analysis.


A great deal of experience in medical flight control of an orbiting astronaut was obtained through the use of the many range, simulations and the several actual flights. The participation in simulations and in flights prior to those which were manned proved to be extremely valuable training exercises for the actual missions. The medical flight controller has indeed shown himself to be a valuable member of the flight control team. The development of mission rules to aid in flight control was necessary in the medical area just as in the many engineering areas. It is difficult to establish definite number-value cut-offs for various medical parameters, but this was done early in the program. Gradually, these rules were made less specific so that the evaluation and judgment of the medical flight controller were the prime determinants in making a decision. The condition of the astronaut as determined by voice and interrogation rather than physical parameters alone became a key factor in the aeromedical advice to continue or terminate the mission. This is as it should be and follows the lessons which were learned in general medicine wherein numerical laboratory values are not necessarily the final answer. Trend information as shown by at least three stations was shown more reliable than single values. In developing the flight-control philosophy prior to the first manned flight, it was thought that it would be necessary for the flight surgeon to talk directly to the astronaut very frequently in order to evaluate his physiological state. As operational experience was gained, it became obvious that this was not the case. Information inquiries were passed easily and smoothly through the spacecraft communicator with the flight surgeon retaining the privilege of talking directly should the need arise. It was also thought early in the program that the occurrence of most any medical emergency in flight would require an early or even a contingency landing. Again, as operational experience was gained with the range and with the planned recovery operation, it was determined that the best philosophy was one which held that the astronaut was in a very fast, air-conditioned ambulance on 100-percent oxygen and in most instances it would be better to return him in the spacecraft to a planned recovery area rather than to abort the flight in a contingency area where it might take hours or days to recover him.


The physiological parameters monitored and the sensor changes and problems may be summarized in the following manner. Body temperature was monitored in all missions through MA-9 with a rectal thermistor. Rectal temperature was found to be the most reliable measurement. The long duration of the last flight and a desire for more comfort resulted in this thermistor being modified for oral use. The range of the thermistor was also changed, so that when it was in the stowed position on the right ear mud it would record suit-outlet temperature. It worked very satisfactorily in this manner.


Respiration was at first measured by an indirect method by using a linear potentiometer and carbon-impregnated rubber. This method was changed early in the program to a thermistor kept at 200° F and placed on the microphone pedestal in the helmet. Neither of these methods gave reliable respiration traces during flight, and a change was made to the impedance pneumograph for the Past two missions. This device gave very accurate respiration information during most of the flight.


Electrocardiographic electrodes were of a low impedance to match the spacecraft amplifier. They were required to record during body movements and to stay effective during flight durations of over 30 hours. These electrodes functioned well and gave very good information on cardiac rate and rhythm. The value of having two leads of electrocardiograph, even though they differed from the standard clinical leads, was repeatedly shown. This allowed easier determination of artifacts and was most helpful in determining the valid sounds on the blood-pressure trace by comparison with the remaining ECG lead. The electrode paste was changed from 30-percent calcium chloride in water mixed with bentonite to a combination of carboxy polymethylene in Ringer's solution.


[205] The ten times isotonic Ringer solution not only retained the necessary conductivity and low impedance required, but also afforded decreased skin irritation after prolonged contact.


In 1958, the obtaining of blood pressures in fight was considered and then delayed as no satisfactory system was available. Definitive work began about the time of the Mercury Redstone 3 (MR-.3) flight, and the automatic system which used the unidirectional microphone and cuff was developed for use in the orbital flights. This system without the automatic feature was used on the MA-6 mission of Astronaut Glenn. During the MA-7 mission, all of the inflight blood pressures obtained were elevated, and an extensive postflight evaluation program was undertaken. It was determined that the cause of these elevations was most likely instrumentation error resulting from the necessity for very careful gain settings matched to the individual astronaut along with the cuff and microphone. A great deal of preflight calibration and matching of these settings was done prior to the MA-8 flight; and on both MA-8 and the last mission, MA-9, very excellent blood-pressure tracings were obtained.


Voice transmissions have been a very valuable source of monitoring information. The normal flight reports and answers to queries have been used for evaluation of the pilot. In order to insure that the monitors were familiar with the astronaut s voice, tapes of mission simulations with the flight astronaut as a pilot were dispatched to all of the range stations for use in preflight simulations. In addition to normal reports, verification of actual comfort level was very valuable in determining the importance of temperature readings obtained by way of telemetry. Inflight photography and, on the last mission, television views of the astronaut have been planned as additional data sources. In Mercury experience, both of these sources have proven to be of very little value in the medical monitoring of the astronaut because of poor positioning of cameras and varying lighting conditions resulting from the operational situation. A full face view of the astronaut in color on a real-time basis would be a good monitoring tool for it would approximate the clinical face-to-face confrontation of the patient.


The value of the comparison of multiple physiological parameters and their correlation with environmental data has been repeated!, proven. Abnormal or lost values attributed to instrumentation difficulty have frequently been obtained, but it has been found that interpretation of the astronaut's physiological condition could be made by the use of the parameters remaining or the correlation of those remaining with environmental data.


It has been interesting to note that a satisfactory amount of information on current astronaut status can be obtained with the use of such basic vital signs or viability measures. It is realized that the monitoring methods may be far from ideal. They did not provide the ultimate in the measure of man's physiological status. It would have been desirable to have a single parameter which would tell the ground monitor whether the nervous system of the pilot was capable of the peak mission performance necessary. To date, however, there is no such single or even multiple measures; and an attack must be made upon this problem from the periphery. It is believed that at present the raw physiological data cannot be replaced by computer evaluation. The basic idea of computer reduction has merit, and help is certainly needed in relieving ground medical monitors of long periods of observation. At present, however, there appears to be no useful system to meet this demand.


In the postflight report on the MR-3 mission (ref. 3), it was stated that "the remote monitoring on a noninterference basis of parameters such as temperature, respiration, the electrocardiogram, and blood pressure in active men fully engaged in prolonged and exacting tasks, is a new field. Hitherto, flight medicine has accepted the information concerning the well-being that could be derived from the pilot's introspection and conveyed by the invaluable voice link. For the rest it has relied on performance to tell how close the man was to collapse. It is to be hoped that some of the developments in automation necessitated by Project Mercury will find application in clinical medicine."


This hope is rapidly coming to fruition in the light of the wide activities in medical monitoring now being carried on in everyday medicine.


[206] Physiological Responses to Space Flight


One of the basic objectives of the Mercury flights was the evaluation of man's physiological responses to exposure to this space-flight environment. These responses also had implications as to his performance capability in this environment. The stresses of this environment to which physiological responses are elicited include the wearing of the full- pressure suit although not pressurized in flight, confinement and restraint in the Mercury spacecraft with the legs at a 90° elevated position, the 100 percent oxygen 5-psi atmosphere, the changing cabin pressure through powered flight and reentry, variation in cabin and suit temperature, the acceleration force (g force) of launch and reentry, varying periods of weightless flight, vibration, dehydration, the performance required by the flight plan, the need for sleep and for alertness, changes in illumination inside the spacecraft, and diminished food intake.


Sources of data used in evaluating these responses have included the control baseline data previously referred to, data from the biomedical sensors received at both the Mercury Control Center and the range stations, voice responses at these stations and the detailed onboard tape, the film record of the onboard tape, answers to debriefing questions, and the detailed postflight examination.


In considering these physiological responses, it was found necessary to have a detailed inflight event history since the peak physiological responses are closely related to critical inflight events. This meaningful relationship is very well demonstrated in considering the pulse responses to the Mercury flights. The peak pulse rates during the launch phase has usually occurred at sustainer engine cut-off. This peak value has ranged from 96 to 162 beats per minute. The peak rates obtained on reentry have ranged from 104 to 184 beats per minute. This peak usually occurred immediately after obtaining peak reentry acceleration, or on drogue parachute deployment. Pulse rates obtained during weightless flight have varied from 50 to 60 beats per minute during the sleep periods to 80 to 100 beats per minute during the normal wakeful periods. (See table 11-I.) Elevated rates during weightless flight can usually be related to flight- plan activity. The respiratory

Table 11-I. Pulse Rates.


SECO (Peak)

Weightlessness (Range)

Reentry (Peak)



108 to 125




150 to 160




88 to 114




60 to 94




56 to 121




50 to 60 (sleep)

60 to 100 (awake)


rates have ranged from 30 to 40 breaths per minute at sustainer engine cut-off, from 8 to 20 breaths per minute during weightless flight, and from 20 to 32 breaths per minute at reentry. Changes noted in the electrocardiograms have included alterations in the pacemaker activity with wandering pacemakers and aberrant rhythm including atrio- ventricular nodal beats and rhythm, premature atrial and ventricular contractions, sinus bradycardia, atrial rhythm, and atrio-ventricular contraction. All of these ''abnormalities'' are considered normal physiological responses when related to the dynamic situation in which they were encountered. Inflight blood-pressure values and body- temperature readings have all been within the physiologically normal range.


The six astronauts who have flown have shown themselves capable of normal physiological function and performance during the acceleration of launch and reentry. The launch accelerations are those imposed by the Redstone and the Atlas launch vehicles. These impose a peak transverse acceleration load of 11g in the case of the Redstone and 7g to 8g in the case of the Atlas.


The vibration produced by launch or reentry has been well tolerated in all cases.


There has been no conclusive evidence of disorientation during flight; and while the astronaut may not have been oriented with respect to the earth, he has always remained so with respect to his spacecraft. The lack of earth orientation has posed no problem whatsoever. There has been no evidence of motion sickness in any of the flight astronauts.


The heat loads imposed by the environmental control system have on occasion caused discomfort but have not been limiting factors in the [207] missions to date. The heat loads and decreased water intake have resulted in postflight dehydration. It has been learned that thermal control in the environmental system is of critical importance.


The Mercury missions were originally planned for altitudes which would not involve contact with the Van Allen Belt of radiation. It was therefore believed that radiation posed no problem in the conduct of these missions, and this was the case until the mall-made radiation belt w-as noted just prior to the MA-8 mission. Personal dosimeters were added within the astronaut's suit and inside the spacecraft at this time in addition to the film packs which had originally been carried. The results obtained from this dosimetry on the last two lights revealed that the astronauts have received no more radiation dose than they would have received had they been here on earth and certainly less than that received during a chest X- ray.


The Mercury program has provided incremental exposures to weightless flight in order to obtain information on which to base predictions of reactions to more prolonged exposures. The crews have uniformly reported that the condition is extremely pleasant and restful. In fact, most of the crews think that it is the only time they have been comfortable in a pressure suit. They have conducted complex visual motor coordination tasks proficiently in the weightless environment. No evidence of body system disfunction has been noted during the period of weightless flight through any of the means of monitoring at our disposal. Food, in cube, liquid, and reconstituted freeze-dried forms, has been eaten normally. Urination has occurred quite normally in timing and amount, and there is no evidence of difficulty in intestinal absorption in the weightless state. Our one experience with sleep periods has raised the question as to whether brief periods of sleep in the weightless condition are more restful than the same periods in a 1g atmosphere. The MA-9 astronaut feels that they are. There is also some question concerning the effect of such a relaxing condition as weightlessness because a number of unscheduled naps occurred. This question will require further investigation on other flights. In the missions to date, there has been no evidence of the mobilization of calcium.


On the last two missions, some postflight orthostatic hypotension, or changes in blood pressure and pulse rate with change in body position, has been noted. This postflight condition has been investigated by the use of the tilt table during the last mission and these results confirm what was only a suspicion on the previous mission. Symptoms of faintness occurred following egress from the spacecraft, and the changes in blood pressure and pulse rate were present for some 7 to 19 hours after landing. In both instances, these changes have been present up until the astronaut retired for the night, a time period of approximately 7 hours; and they have always disappeared by the time of the first check after the astronaut has awaken. Thus, the orthostatic changes have lasted no longer following the more prolonged flight in the MA-9 mission than for the shorter flight; and in both instances, blood pressure and pulse rate have returned to normal while the astronaut was at bed rest. These findings do cause concern about prolonged exposure without some interim steps for further evaluation of this condition.




The medical support of the overall Project Mercury recovery operation had to meet two basic requirements:

(1) The capability of providing prompt, optimum medical care for the astronaut, if necessary, upon his retrieval from the spacecraft.

(2) The provision for early medical evaluation to be made of the astronauts postflight condition.


It was considered essential to establish a medical capability for any circumstance under which recovery could occur. The general concept was to provide the best care in the fastest manner possible. Details of the medical recovery requirements may be found in the appropriate NASA documents (refs. 1, 4, 7, 10, and 12). The original plans were necessarily based on anticipating the direst situation expected, and very correctly so. The extent of medical care which could be effectively administered to the astronaut during the recovery operation is governed to a large degree by the physical circumstances under which recovery occurs. Consequently, the level of medical support necessary at the different recovery areas varies [208] according to the potential extent to which competent medical treatment can be administered in that area, and the most extensive medical support is properly concentrated in those areas where descent to earth by the astronaut is most probable. Access times for the various recovery areas were determined to be medically acceptable time periods to allow reasonable protection of the astronaut based upon accumulated knowledge of human survival, need for medical attention, and reaction to physiologic stress. Since the recovery forces are routine operational units diverted to this operation by the Department of Defense, it also became obvious that the medical support must be obtained through the cooperation of the Department of Defense. Civilian physicians are not available for deployment for the necessary time periods. It will be noted that one of the basic philosophy changes during the program involved a change in emphasis from taking medical care to the astronaut in the early missions to provisions for returning the astronaut to definitive medical care in the later missions. The medical support was provided for three basic categories:

(1) Rapid crew egress and launch-complex rescue capability during the late countdown and early phases of powered flight.

(2) Positive short-time recovery capability throughout all phases of powered flight and landing at the end of each orbital pass.

(3) Reduced capability in support of an unplanned landing along the orbital track.


In the launch-site area, this support included a medical-specialty team consisting of a general surgeon, an anesthesiologist, surgical technicians and nurses, a thoracic surgeon, an orthopedic surgeon, a neurosurgeon, an internist, a radiologist, a pathologist, a urologist, a plastic surgeon, and supporting technicians. In the early missions, these individuals were deployed to Cape Canaveral and were available should the need arise for their use either at Cape Canaveral or, in the event of a requirement for their services in the recovery area, they could be dispatched by aircraft. On the last two missions, it became necessary to develop a team at Tripler Army Hospital, Hawaii, to cover the Pacific area as well as a team deployed to Cape Canaveral to cover the Atlantic area. It became obvious that there were large numbers of highly trained physicians who were merely waiting out the mission in a deployed state with an unlikely probability that they would be utilized. Careful evaluation of the experience and of sound medical principles involving emergency medical care led to the conclusion that the specialty team could be maintained on standby at a stateside hospital and easily flown either to Cape Canaveral or a recovery site if their services were needed. There were surgical resuscitatives teams available at these sites. Other launch-site support was provided by a point team consisting of a flight surgeon and scuba-equipped pararescue personnel airborne in a helicopter. Medical technicians capable of rendering first-aid care were also available in LARC vehicles and in a small water jet boat stationed on the Banana River. A surgeon and an anesthesiologist with their supporting personnel were stationed in a blockhouse at Cape Canaveral to serve as the first echelon of resuscitative medical care in the event of an emergency. Physicians were stationed throughout the recovery areas aboard destroyers and aboard one aircraft carrier in the Atlantic and one in the Pacific. In the early missions each vessel was assigned a surgeon, anesthesiologist, and a medical technician team with the supporting medical equipment chest necessary for evaluation and medical or surgical care. As confidence was gained in the operations, this distribution was modified to assigning only a single physician, either surgeon or anesthesiologist, to the destroyer. Attempts were made to place a surgeon on one and an anesthesiologist on another vessel nearby. This would allow their teaming up if necessary. The general concept was, however, that they would provide resuscitative care only and then evacuate the astronaut to the carrier in their particular area. The carrier was provided a full surgeon, anesthesiologist, technician team. Hospitals along the orbital track were alerted for their possible use, and some near planned landing areas were briefed by NASA- DOD teems. These briefing are thought to be extremely valuable aids in assuring adequate medical support. Early in the missions, blood was drawn from donors and made available for transfusion at Cape Canaveral and in the recovery area. As the operation grew wider in scope involving the Pacific, and as more confidence was gained, dependence was [209] placed upon walking blood bank donors who were typed, and drawn blood was available only in the launch site area.


Acknowledgements.-The author wishes to acknowledge the invaluable contributions of Stanley C. White, M.D., William K. Douglas, M.D., Carmault B. Jackson, M.D., James P. Henry, M.D., David P. Morris, M.D., and the staff of the Life Systems Division of the original Space Task Group. Special gratitude is extended for the professional advice and assistance of the medical monitors who served as the eyes and ears of the MCC Surgeon at the range stations, the many DOD physicians and their supporting DOD personnel who served on evaluation, specialty, and recovery teams, and the entire staff of the Center Medical Operations Office.




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